1. Field of the Invention
This invention relates to computer systems and, more particularly, to replication in storage environments employing distributed block virtualization techniques.
2. Description of the Related Art
Many business organizations and governmental entities rely upon applications that access large amounts of data, often exceeding a terabyte or more of data, for mission-critical applications. Often such data is stored on many different storage devices, which may be heterogeneous in nature, including many different types of devices from many different manufacturers.
Configuring individual applications that consume data, or application server systems that host such applications, to recognize and directly interact with each different storage device that may possibly be encountered in a heterogeneous storage environment would be increasingly difficult as the environment scaled in size and complexity. Therefore, in some storage environments, specialized storage management software and hardware may be used to provide a more uniform storage model to storage consumers. Such software and hardware may also be configured to add storage features not present in individual storage devices to the storage model. For example, features to increase fault tolerance, such as data mirroring, snapshot/fixed image creation, or data parity, as well as features to increase data access performance, such as disk striping, may be implemented in the storage model via hardware or software.
In order to protect against a complete loss of such a storage environment (e.g., in the event of a natural disaster or a terrorist attack), it may be desired to implement a disaster recovery plan and/or system. A common technique that may be employed for disaster recovery in some environments is the production of tape-based data backups periodically (e.g., once a day) at a primary data center for shipment to an offsite or secondary data center. The storage environment of the primary data center may be replicated if needed at the secondary data center using the tape-based data backups. However, producing tape-based backups of a large, distributed storage environment handling frequent updates may be unacceptably slow for some data centers, and the time taken for recovery using a tape-based solution may also be unacceptably long. In order to speed up replication, hardware storage devices designed specifically for rapid replication operations (such as hardware snapshot devices) may be employed in other storage environments. This approach may also have drawbacks: for example, different hardware replication devices may be incompatible with each other, and the owner of the storage environment may prefer not to be tied to a specific hardware device vendor. Furthermore, hardware replication devices may not allow users the flexibility of replicating a subset of data, rather than the entire set of data, located on a given storage device, some of which may not be required for disaster recovery. A hardware-device-independent mechanism that allows storage consumers to flexibly and quickly replicate the data of a complex distributed storage environment may therefore be desirable.